Macro term 

macro_rules! term {
    (<$ident:ident>) => { ... };
    ($ident:ident) => { ... };
    ($ident:literal) => { ... };
}

Creates a Terminal if the input is a string literal or a Nonterminal if the input is inside angle brackets

bnf::term!("terminal");
bnf::term!(<nonterminal>);